The invention relates to a locking mechanism for telescoping sections of an apparatus such as a crane boom.
Crane boom telescoping sections may be lockable in the extended condition to relieve the load that would otherwise bear on the telescoping system, among other things. This is called for in particular when entraining means, for example piston/cylinder units, are use to extend the telescoping sections, which extend and retract one telescoping section after the other in sequence. Locking telescoping sections is generally achieved by locking bolts which are mounted on one telescoping section and engage in a receiving location of an adjoining telescoping section.
DE 198 11 813 A1 discloses a locking mechanism, in which two respective locking bolts of a locking unit are arranged on an inner telescoping section so that they can be made to engage two opposing receiving locations in the vertical side webs of the adjoining outer telescoping section. The locking mechanism comprises a hydraulic cylinder, arranged parallel to the longitudinal centerline of the telescoping sections, and a lever which shifts the locking bolts upon movement of the actuating cylinder. The engaging end of the lever engagesxe2x80x94when the device is positioned at a suitable location as controlled by a position monitorxe2x80x94the inner clasp of the locking bolt so that the locked position can be released by actuating the hydraulic cylinder. The minimum dimensions necessary for the innermost telescoping section are dictated by a) the configuration by the engaging end of the lever and of the inner clasp of the locking bolt, b) the travel necessary to overcome the spacings between outer and inner telescoping section as well as c) the minimum dimensions as dictated by the strength and functioning requirements involved for the locking bolts, their mounting, the clasps of the locking bolt, the lever as well as the actuating cylinder.
It is an object of the present invention to provide a locking mechanism for telescoping sections which takes up significantly less room than known devices. An object is to enable use of such locking system in substantially smaller telescoping sections of crane booms than hitherto possible. In addition, an object of the invention is to provide a simple and cost-effective locking mechanism for telescoping sections.
In accordance with the invention, a locking mechanism for telescoping sections comprises a linearly shiftable locking bolt for connecting and releasing an inner telescoping section and an outer telescoping section, the locking bolt being maintained biased in its extended position and shifted by means of a rotary actuator from its extended position into its retracted position.
An advantage of an assembly in accordance with the invention is that it can be constructed with relatively small, overall dimensions. Both the height and width of the space required are significantly reduced by using a rotary actuator. Thus, the locking system can be used on substantially smaller telescoping sections of crane booms than hitherto possible. Alternatively, or additionally, the invention frees up space within the confines of a telescoping boom section that may be devoted to other components and/or structural considerations.
The locking bolt may be mounted in an inner telescoping section and protrude in its extended position into the adjoining outer telescoping section so that the telescoping sections cannot be shifted relative to each other axially. In its retracted position, the locking bolt is out of engagement with the outer telescoping section permitting shifting of the telescoping sections relative to each other. Instead of a hydraulic cylinder, a small rotary drive may be used. This rotary drive may be powered in any way, such as hydraulically, electrically or pneumatically. A rotary drive of this kind takes up much less room than a hydraulic cylinder acting on the locking bolt by means of a system of levers. It is particularly preferred to arrange two locking bolts on an inner telescoping section so that they are engageable with two opposing receiving locations in the vertical side webs of the outer telescoping section, i.e. preferably in the middle portion of the side webs.
The rotary actuator may act directly on the locking bolt. It is particularly preferred that the locking bolt is connectable at least temporarily to the rotary actuator via a connecting element.
In a preferred embodiment, the connecting element comprises or is formed as a cam guide or a cam claw. This is particularly advantageous when the connecting element is not intended to be permanently connected to the locking bolt. The cam guide is driven by the rotary actuator to act on the locking bolt which, in keeping with the configuration of the cam of the cam guide, is linearly shifted. Preferably, a cam guide or cam claw is provided which comprises a guiding surface area and which may be easily brought into or out of engagement with the locking bolt. In a particularly preferred embodiment the cam guide is a cam plate.
In a preferred embodiment the invention includes an engaging member associated with the locking bolt, for example, in the form of a pin or a roll. The rotary actuator rotates about an axis that is substantially perpendicular to the direction of shifting of the locking bolt along its own axis. Upon turning of the cam guide, the guiding surface area moves along the engaging member so that the locking bolt is drawn towards and approaches the axis of the rotary actuator.
In accordance with the invention, the cam guide may be preferably disengaged from the locking bolt. This is particularly of advantage when the same rotary actuator and cam guide are to be used for different locking bolts of different telescoping sections. It is particularly preferred that the cam guide can only be disengaged from the locking bolt when the locking bolt is in its extended (locked) position. This enhances the operating safety of a locking action, since the inner telescoping section is never in a xe2x80x9cfreexe2x80x9d state, that is, a state in which the inner telescoping section is connected neither to the outer telescoping section nor to the cam guide. The cam guide can then be caused to engage and disengage respectively with the locking bolt when the locking bolt is in its xe2x80x9csafexe2x80x9d extended position.
Preferably, in accordance with the invention, the cam guide can be brought into a passive position, in which the cam guide is disengaged from the locking bolt, and can be shifted relative thereto without engaging the locking bolt. Preferably, the cam guide is locked in its passive position to prevent unintended rotation to enhance safety. Thus, an accidental actuation or disengagement of a locking bolt from a locked position is prevented.
In order to shift the telescoping sections relative to each other, a piston/cylinder unit is typically used. In a typical arrangement the head of the cylinder is connectable with the inner telescoping section and shifts it relative to the outer telescoping section upon actuation of the cylinder. Prior to the inner telescoping section being shifted, the lock between the two telescoping sections is released by moving the locking bolt into its retracted position. Preferably, a release device is provided which is connected to the piston/cylinder unit, preferably at the head of the cylinder at the piston outlet end, and can be shifted along the centerline of the telescoping sections. The release device comprises the rotary actuator and the connecting element and is engageable with the inner end of the locking bolt in order to move the locking bolt against the biasing action from its extended locked position into its retracted disengaged position.
In order that the engaging member of the locking bolt can be caused to reliably engage the guiding surface area of the rotary actuator, the locking bolt is preferably mounted so that it is linearly (axially) shiftable and non-rotatable. A locking bolt having a cornered or oval cross-section may be used. If a cylindrical locking bolt is used, it may be prevented from turning by a groove or a pin.
The cam guide may be held in its passive position by an elastic force, in particular by a spring force. The cam guide can be fixedly located in the passive position by a locking element, in particular a locking pin. The locking element may be employed in addition to the spring force.
By suitably configuring the cam guide and selecting the passive position, the width of the locking mechanism can be reduced to such an extent to reliably avoid any collision with surrounding parts of the locking bolt and parts of the telescoping sections during movement of the piston/cylinder unit in the longitudinal direction of the telescoping sections.
In accordance with another aspect of the invention, the locking bolt may be received or mounted in a receiving location, particularly a bush or bushing, in which an emergency actuator is provided for shifting the locking bolt from its extended position into its retracted position. Thus, an emergency actuator for releasing the locking bolt without the rotary drive is integrated in the receiving location of the locking bolt. Such a feature saves additional space in construction of an apparatus in accordance with the invention. The emergency actuator may comprise an actuating element, in particular a pin, held in the bushing in various axial positions in the axial direction thereof and entraining the locking bolt upon a change in its axial position. The actuating element may be held clamped in various axial positions. It is particularly preferred that the emergency actuating element is connected to the bushing via a screw thread, and can thus be positioned in various axial positions relative to the bushing upon rotation. For this purpose, the actuating element is connected via a screw thread to the side of the bushing facing the cam guide. When the actuating element is fixedly located at the locking bolt and turned around its longitudinal centerline, the screw thread creates a relative movement between the locking bolt and bushing. Configuring the emergency actuator in this way with the bushing integrated in the actuator unit requires substantially less constructional room compared with prior art.
Another preferred aspect of the invention is that the emergency actuator may be configured so that it can be used also as a rotary lock preventing the locking bolt from rotating. Accordingly, the actuating element may be used as an emergency actuator, as a rotary lock or both. The emergency actuator or rotary lock, previously described, may also be used to advantage without a rotary actuation of a cam guide for shifting the locking bolt.
Preferably, the proximity sensors for sensing the relative position of the telescoping sections are directly integrated in the cylinder head. For this purpose, the cylinder head is configured so that the proximity sensors are accommodated in cavities or holes in the cylinder head and electrical connections can be brought out via cable guides inserted in the face of the cylinder head. This results in the proximity sensors taking up little room while, at the same time, accommodating them in a protected manner.